Especially titanium aluminides are considered an optimum material in various areas of application because of their low density, relatively high-temperature, specific strength relative to nickel superalloys, and corrosion resistance. However, materials with a narrow range between solidus and liquidus temperature, like TiAl or pure titanium grade 2, are very difficult to shape, the only practical method for forming them is to cast them.
When casting such materials one is encountered with further problems like an unusual high amount of shrinkage of the intermetallic phase (γ-TiAl) during solidification resulting in the formation of shrinkholes, voids, pores, etc. in castings. This makes it usually necessary to reprocess the casting by expensive high-pressure compaction (HIP method).
Further, when casting such materials in molds having a complicated geometry, like shrouded tubine blades, the casting frequently shows damages shows damages like cracks, e.g. hot tears, or even torn off blade shrouds. These are strain induced damages corresponding to a rapid shrinkage during the solidification process.